1. Field of the Invention
The invention relates to a block execution sequence display system for a numerical control device and a programmable controller for, for example, a machine tool.
2. Discussion of Background
In a machine tool, conventionally, a numerical control device is used to carry out axis control, and a programmable controller is used to control miscellaneous operations of, for example, miscellaneous equipments, other than the axis control. A program used in the numerical control device is a numerical control (NC) program written in a numerical control (NC) language. A program used in the programmable controller is a sequence program written in a program language, such as a ladder circuit diagram and a sequential function chart (SFC program). The ladder circuit diagram is a logical combination of signals by contacts and coils, and is suitable for visual recognition of a control circuit. The SFC program is written in a graphical program language that indicates a program in a plurality of divided steps in a flowchart form, and is suitable for representing the execution sequence and execution conditions of a program. The NC program and sequence program are programmed such that a series of operations are executed in a specified operation sequence by controlled axes and miscellaneous equipments that operate in association with each other.
A machine tool is often provided with a monitoring device as a peripheral device to, for example, monitor the operating states of such a numerical control device and a programmable controller, detect an abnormal or faulty portion, and debug a program. In a monitoring device for a programmable controller that uses a SFC program, as described in U.S. Pat. No. 5,426,730, the SFC program is graphically displayed on, for example, a display, and an active step or transition is displayed with, for example, a background color different from that of the other portions. Thus, an operator is able to visually recognize a currently executed portion of the SFC program easily. Therefore, for example, detection of an abnormal or faulty portion is facilitated.
However, in a machine tool in which control is executed by a combination of a numerical control device and a programmable controller, a control program is formed of a NC program and a sequence program that are different in type. Therefore, the execution sequence and execution status are not easily recognized with the use of a monitoring device. For example, the execution sequence of processes shown as steps in a SFC program is easily understood from the displayed information. However, with regard to processes of NC program operations included in a series of processes, the contents and execution sequence of a NC program are not easily visually recognized. The monitoring device is able to display a control circuit formed of, for example, a ladder circuit that is an action associated with a step when the step in the SFC program is selected. However, when a step associated with a NC program operation is selected, a control circuit that starts up the NC program is displayed, and the contents of the NC program are not visually recognized. Therefore, in order to visually recognize the contents and execution sequence of a NC program, the NC program is separately retrieved, and the contents and execution sequence of the NC program are understood from the displayed NC language. Therefore, visually recognizing the contents and execution sequence of a NC program takes time and effort and requires knowledge about NC language.
In order to, for example, detect an abnormal or faulty portion or debug a program, the contents of a sequence program need to be checked from a NC program in some cases. For example, a command for miscellaneous equipment, written within a NC program and called an M code command, corresponds to an input condition for a control circuit for the miscellaneous equipment. The entity of the control circuit for the miscellaneous equipment is present in a program portion formed of, for example, a ladder circuit diagram that differs from the SFC program within the sequence program. Therefore, in order to check the contents of the sequence program that corresponds to the M code command from the NC program, the program portion formed of, for example, the ladder circuit diagram needs to be separately retrieved and the control circuit for the miscellaneous equipment, which corresponds to the M code command, needs to be found from the displayed circuit. This is not easy. In a situation where a trouble occurs in a machine tool and the cause of the trouble has to be found as soon as possible, if a lot of time is consumed to find a stop point of the NC program and a control circuit, a manufacturing line stops for a long time.